The present invention relates to methods and devices for cutting an adhesive film mother sheet wherein an adhesive layer is covered by a base film and a cover film. Specifically, the present invention relates to techniques for preventing or reducing the peeling of the cover film from the adhesive layer when cutting an adhesive film mother sheet while the cover film is bonded to the adhesive layer by a relatively small adhesive force.
Adhesive film, wherein both sides of an adhesive layer are covered by a base film and a cover film, is generally used when joining substrates to each other within multilayer printed circuit boards.
The process of bonding together two substrates using such an adhesive film comprises the peeling of the cover film from the adhesive layer to expose a surface of the adhesive layer and attaching one of the substrates to the exposed surface of the adhesive layer, and then peeling of the base film from the adhesive layer to expose another surface of the adhesive layer and attaching the other substrate to that exposed surface.
Treatment to ensure that the base film and the cover film can be removed by peeling is performed through the formation of a silicone film between the base film and the adhesive layer, and between the cover film and the adhesive layer. If, as described later, the adhesive force is denoted as the force required to peel the cover film or the base film respectively from the adhesive layer, then the adhesive force to the cover film is ordinarily set smaller than that of the base film so that the cover film can be more easily peeled from the adhesive layer.
Furthermore, in the process for manufacturing the adhesive film, a cutter mechanism is pressed against a long and narrow adhesive film mother sheet that is being conveyed in the longitudinal direction thereof, the adhesive film mother sheet is cut in that longitudinal direction, and adhesive films so cut to a narrow width are wound in.
As shown in FIG. 3, the cutting mechanism is, for example, configured such that an upper blade unit 11A having upper blades 11 arranged in an axial direction and a lower blade unit 12A having lower blades 12 arranged in an axial direction mutually engage. JP 2000-326284A (patent document 1) describes a slit device for improving such a cutter mechanism. In the slit device, the lateral pressure between the upper blades and the lower blades is balanced by numerically regulating the spaces between the upper blades and the spaces between the lower blades based on the relationships with the blade widths, in order to reduce the degree of warping in the adhesive films 2a after cutting.
As shown in FIG. 3, the adhesive film mother sheet 2 is cut as a result of sliding contact between the side surfaces of the upper blades 11 and the side surfaces of the lower blades 12. Shearing forces act on the cut surface edges of the adhesive films 2a formed by cutting of the adhesive film mother sheet 2 in this way, and the adhesive film 2a above a lower blade 12 is bent in a convex shape and the adhesive film 2a below an upper blade 11 is bent in a concave shape.